1. Field of the Invention
This invention relates to a manufacturing method of a semiconductor device.
2. Description of the Related Art
It is important to reduce the capacitance between wires, that is, lower the dielectric constant of insulating films in order to enhance the operation speed of a semiconductor device. An organo-siloxane film is widely used as the insulating film with the low dielectric constant, but it is proposed to use a porous insulating film having fine voids in the film to further lower the dielectric constant (for example, refer to Jpn. Pat. Appln. KOHYO Publication No. 2004-509468).
However, since the film density of the porous insulating film is low, etching gas easily penetrates into the film at the dry etching. When a porous organo-siloxane film is used as the porous insulating film, there occurs a problem that Si—O bonds and Si—CH3 bonds in the film are broken by the etching gas and the film quality is degraded. The moisture absorbency of the porous organo-siloxane film increases due to the degradation of the film quality and this causes the characteristic of the semiconductor device to be degraded.
Thus, the porous organo-siloxane film is proposed as the insulating film with the low dielectric constant, but it is conventionally difficult to attain a porous organo-siloxane film of high quality.